1. Field of the Invention
The present invention relates to pipe testing, and more particularly relates to a method and apparatus for the testing of connected pipe joints by the application of interior hydrostatic pressure.
2. General Background and Prior Art
In the oil and gas, as well as related industries, it is desirable to utilize pipe and pipelines for the transmission of products on the interior portion thereof either from wells and the like or from production platforms to central points of collection.
Often pressure within pipelines through which liquids are transmitted are, by design or otherwise, excessively high. Therefore, a need exists for a device which can quickly inspect and test under pressure a pipeline or like conduit through which fluids under pressure are to be transmitted. It is especially important that the joints between sequential pipe sections be tested. This is true because the quality of individual pipe sections is substantially well controlled during manufacture. Therefore, hydrostatic pressure performance characteristics are quite predictable, resulting from strict manufacturing techniques. However, the individual joints are generally field connected under less exact conditions and require a much closer inspection before actual use. Under field conditions, pipes can become abused or simply are not connected properly, thus needing adequate testing before operation. It is to this problem that the present invention is directed.
Several devices have been patented which have attempted to provide a device for the testing of pipes and connected pipe joints. The following table lists some devices which have been patented.
______________________________________ Prior Art Patents U.S. Pat. No. Inventor(s) Issue Date ______________________________________ 2,998,721 P.A. Gawlik Sept. 5, 1961 3,038,542 G.L. Loomis June 12, 1962 3,173,290 G.E. Conover Mar. 16, 1965 3,199,598 G.L. Loomis Aug. 10, 1965 3,333,459 J.R. Claycomb Aug. 1, 1967 3,354,697 J.P. Wilkerson Nov. 28, 1967 3,420,095 N.F. Brown, et al Jan. 7, 1969 3,899,920 C.J. Matherne Aug. 19, 1975 ______________________________________
Some of the devices of the prior art utilize a hydraulically activated "piston" which pushes against a rubber "packing seal", thereby compressing the seal, and expanding it to effect a seal between the tool and the pipe diameter. Two of these "packing seals" are then utilized on a single testing device to form a fluid tight test chamber between the seals at the joint to be tested. Several problems have been experienced with this type of sealing device. The packing seals, being made generally of a rubber or other synthetic flexible material, sometimes "run" over the edges of the sleeves which act to compress the seals themselves. This happens because the seal or packer itself is only being pushed by one piston, and is thus urged away from its location on the tool body.
Another problem is that the seals can only expand a certain distance, and thus cannot be used with some larger diameter pipe sizes. Many times the "packer" effects a seal of the pipe, but the rubber or synthetic material, in "running" over the edge of the sleeve causes the device to become stuck inside the pipe it is testing. This is especially true where a tool is used to test a pipe which is larger than what it can normally test. Thus, it can be seen that with a given tool, only a small variety of sizes can be tested.
Another problem of the devices of the prior art relate to the replacement of damaged parts. Since pipe testers of the present type utilize two packing seals which form water tight seals on either side of a joint to be "tested", it can readily be seen that the failure of one "seal" renders the entire device ineffective.
The present invention solves all these prior art problems and shortcomings in a simple but effective manner. In the present invention, there are provided packing seals which are longer than the prior art devices, and are compressed with two hydraulically activated pistons on a single packing seal. Additionally, the rubber packing seals are bonded to the metal on which they are mounted, thus reducing the chance for "run over" of the packing material on top of the piston, thus jamming the device inside the pipe to be tested.
The use of two pistons operating on a single rubber seal permits the device of the present invention to be utilized in a variety of pipe diameters, substantially larger than could be tested by similarly sized devices of the prior art. Since two pistons act simultaneously on one packer, the packer is not "urged" away from its location on the tool body, thus further reducing the chance for "run over".
Additionally, the interface of the piston and packer is an angular interface, with the piston edge coverably overlapping the packer to further reduce run over when the pipe testing apparatus of the present invention provides tool sections having packing seals which are interchangeable. Thus if either seal on a particular tool is damaged, it can be readily replaced with a single tool body section having a seal thereon which could function as either the upper or lower seal for the entire apparatus.